Infected PCs spew MyDoom variant

Business as usual

Common Topics

The MyDoom worm saga continued today with the release of yet another variant of the noxious email worm. The latest variant - MyDoom-S (AKA MyDoom-Q or MyDoom-R) - poses as a funny photographs in order to dupe users into opening an infectious attachment called photos_arc.exe.

MyDoom-S runs when a Windoze user (Linux or Mac users are immune) clicks on this malicious attachment. Thereafter the worm mass-mails itself to email addresses harvested from the infected machine with the subject line "photos" and message body "LOL!;))))". Like other variants of MyDoom, MyDoom-S also tries to download a backdoor Trojan (in this case Surila-G) from one of a number of websites onto infected PCs. The Trojan allows infected machines to be controlled remotely by attackers in order to send spam, for example.

Finnish AV firm F-Secure reckons virus writers bulk-mailed copies of MyDoom-S from machines infected by earlier versions of the worm in an effort to give their latest creation a kick-start.

In an advisory, F-Secure states: "The source addresses of the spams appear to be from DSL and cable modem pools, suggesting that the MyDoom gang is using a botnet created with earlier MyDoom variants to send this one out. They've also carefully checked that none of the common antiviruses detect this new variant. The worm contains a backdoor. System administrators may also want to block access to domains www.richcolour.com and zenandjuice.com from their network for a while. This variant tries to download components from these addresses but the sites themselves have nothing to do with the virus group."

MyDoom-S began spreading (fairly extensively) today. Most AV vendors rate MyDoom-S as a medium risk threat. MyDoom-S is programmed to stop spreading on 20 August 2004 but the backdoor does not have an expiration date. ®